CharlesGrey: After reading the title of the thread, I instantly thought: "Nope. Not OK." But now that I think about it... If someone was being honest about it, and removed all copies from their own computers before giving a game to a friend, it would be no different from a traditional physical game on disc/cartridge/floppy etc. Of course the recipient of the game wouldn't be allowed to create and give away multiple copies of the game either. But as long as there's only one copy and owner of the game at a time, it would work just like traditional games, right?
True, buf for me there are a couple of things against considering them the same as (lending or giving out) physical games:
1. With physical games, it is harder to make perfect 1:1 copies. So if I give a game CD to a friend, I am more assured he won't be making millions of copies of it and sharing to all his friends, or to the world.
I feel that since I bought the game originally, I am responsible that copies of it are not made available to others. So theoretically I might see myself installing a game to a friend's (or rather, family member's) computer, but not at least giving an installer to them that they could easily share around without me knowing about it.
2. Digital games in general are dirt cheap compared to physical retail games of the past so I also feel people should afford to buy their own copies. I recall back when I felt a discounted retail game costing 10€ is damn cheap so that I just couldn't pass it; nowadays paying 10€ for a digital game feels quite expensive overall.
3. Related to the earlier point, digital games are also more easily available. A store doesn't run out of copies of a digital game, so it can't be either that a friend can't easily find the game in stores anymore (hence, in practice the only way he could play it is either pirate it, or borrow it from me).
If some digital game is completely removed from all stores and never coming back (due to license or whatever), then I might see a reason to "borrow" it to some friend who I feel would enjoy it.